Trying to build bare extension template, VS2010 gives me 'can't access Project1.sdlplugin, used by another process'

I am trying to build an extension for Trados 2014.  It seems as though there are new SDK components, but no new SDK, so I am using the older SDK posted here, which seems to dump its output into SDL\SDL Trados Studio\11 -- is that much right?

I am trying to build the project template with no modifications at all, just to prove I can get that far before I write a line of code.  I generated a strong name with the .NET "sn" tool, and indicated the file generated in both AssemblyInfo.cs and the Project "Signing" properties.

No matter what I do to get around it, including hand-delete steps in the BuildEvents, VS 2010 gives me "MSBUILD : error PFE403: The process cannot access the file 'c:\Users ...... 11\Plugins\Packages\Plug-in Project1.sdlplugin".  Of course, I have done this from a freshly-booted machine and hand-deleted Project1 artifacts in that directory before even bringing up Visual Studio.

Has anyone else encountered this problem? I've seen reports on the web of similar problems with DLL's, but the ways of getting around it don't seem to work for the .sdlplugin file.

Any help would be appreciated, for I can't write the first line of code until this is conquered.

Thanks

Bernie